1. Field of the Invention
This invention relates to a new or improved rotary drive coupling, and in particular to a coupling which is capable of transmitting torque and axial thrust forces of high magnitude, and is also capable of accommodating minor angular misalignments between the driving and driven rotating members.
2. Description of the Prior Art
Drilling apparatus employed for drilling holes into subterranean rock formations must, of necessity, be of rugged construction and capable of applying high torques and high axial loadings to effect satisfactory operation of the cutter head in the rock formation. Such drilling arrangements include a drilling motor coupled to the kelly bar of a drill string and means to remove the rock cuttings from the bottom of the drill hole to the surface, such means normally comprising a flow of fluid directed downwards in passages through the kelly bar and drill string to entrain the cuttings from the bottom of the drill hole and carry them upwards to the surface through a separate passage in the drill string. The drill motor is normally arranged upon a fixed drilling platform mounted on the earth surface. Where the hole being drilled is in an underwater rock formation, then the drilling platform may be mounted upon a floating structure such as a barge or scow, or may be fixedly mounted e.g. upon stilt-like legs resting upon the bed of the body of water. Drilling from a floating platform such as a scow is desirable from the point of view of cost, but entails the difficulty of transmitting the driving torque while accommodating movement of the platform as is occasioned by wind and wave action, tides, etc. Furthermore, with a floating drilling platform it is desirable that the drilling motor should be capable of being disconnected from the kelly bar and drill string quickly so that drilling can be interrputed and the scow removed to safety during adverse weather conditions. Existing drilling systems have not been able to satisfy these requirements.